CN108242546A - A kind of agraphitic carbon negative material and preparation method thereof and battery - Google Patents

Abstract

The invention relates to the field of electrode materials, in particular to an amorphous carbon negative electrode material, a preparation method thereof, and a battery. The preparation method of the amorphous carbon negative electrode material includes: (1) in an oxygen-containing atmosphere, the coal-based pitch is subjected to the first heat treatment; (2) in a vacuum or under the first gas flow rate, the first The product after the heat treatment is subjected to the second heat treatment; (3) the product after the second heat treatment is subjected to the third heat treatment in vacuum or under the second gas flow rate. The amorphous carbon negative electrode material obtained by the method of the invention has excellent rate performance, and also has relatively high specific capacity and rate performance.

Description

A kind of amorphous carbon negative electrode material and its preparation method and battery

technical field

The invention relates to the field of electrode materials, in particular to an amorphous carbon negative electrode material, a preparation method thereof, and a battery.

Background technique

Carbon anode materials are widely used in lithium-ion batteries. At present, the main carbon anode materials are crystalline carbon (including natural graphite, artificial graphite, etc.) and amorphous carbon (including soft carbon, hard carbon, etc.). Among them, the dominant negative electrode material is graphite, which has a relatively regular layered structure, good electrical conductivity, and a theoretical specific capacity of 372mAh/g. However, graphite is limited by its diffusion coefficient. Under the condition of high current charge and discharge, the diffusion rate of lithium ions is not fast, and the rate performance is poor; on the contrary, when amorphous carbon is used as the negative electrode material, the intercalation and deintercalation of lithium ions are relatively free. , the diffusion rate of lithium ions is relatively fast, and the rate performance is high; however, when the usual amorphous carbon is used as an anode material, the specific capacity is low, which restricts the application of amorphous carbon as an anode material.

Contents of the invention

The object of the present invention is to provide an amorphous carbon negative electrode material with a higher specific capacity and a preparation method thereof by optimizing preparation and changing the structure of the carbon material, aiming at the phenomenon that the specific capacity of the existing amorphous carbon is low when used as the negative electrode material.

In order to achieve the above object, the present invention provides an amorphous carbon negative electrode material, the amorphous carbon in the negative electrode material has an amorphous degree of 18-30%, and a Raman _Id / _Ig of 1.01-1.1.

The present invention also provides a method for preparing an amorphous carbon negative electrode material, the method comprising:

(1) In an oxygen-containing atmosphere, the coal-based pitch is subjected to a first heat treatment;

(2) subjecting the product after the first heat treatment to the second heat treatment in vacuum or under the first gas flow rate;

(3) subjecting the product after the second heat treatment to the third heat treatment in vacuum or under the second gas flow rate;

Wherein, the temperature of the first heat treatment<the temperature of the second heat treatment<the temperature of the third heat treatment; and, the temperature of the first heat treatment is 150-400°C, and the temperature of the second heat treatment The temperature of the treatment is 500-850°C, and the temperature of the third heat treatment is 800-1200°C;

The first gas flow rate and the second gas flow rate are each independently more than 30min ⁻¹ m ⁻² , and the gas flow rate is measured by volume space velocity per unit cross-sectional area; and, the first gas flow rate The gas introduced into the input volume and the second gas intake volume is an inert gas.

The invention also provides the amorphous carbon negative electrode material prepared by the above method.

The present invention also provides a battery comprising the above-mentioned amorphous carbon negative electrode material.

By adopting the method of the present invention, the coal-based pitch can be converted into an amorphous carbon negative electrode material with excellent performance. The obtained amorphous carbon negative electrode material has excellent rate performance, and also has high specific capacity and rate performance. The raw material is abundant and easy to operate. Simple and low cost.

Other features and advantages of the present invention will be described in detail in the detailed description that follows.

Detailed ways

Specific embodiments of the present invention will be described in detail below. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

Neither the endpoints nor any values of the ranges disclosed herein are limited to such precise ranges or values, and these ranges or values are understood to include values approaching these ranges or values. For numerical ranges, between the endpoints of each range, between the endpoints of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, these values Ranges should be considered as specifically disclosed herein.

The invention provides an amorphous carbon negative electrode material. The amorphous carbon in the negative electrode material has a degree of amorphism of 18-30%, and a Raman _Id / _Ig of 1.01-1.1.

According to the present invention, the amorphous carbon negative electrode material is actually amorphous carbon. When the amorphous carbon satisfies the degree of amorphism in the above range, it can maintain excellent amorphous carbon state and electrochemical performance. Preferably, the negative electrode The amorphous degree of the amorphous carbon in the material is 20-28% (more preferably 22-25%), and the Raman _Id / _Ig is 1.01-1.1 (preferably 1.02-1.05). Wherein, the degree of amorphousness refers to the degree of crystallinity calculated from the 002 peak of XRD, and the degree of amorphousness is obtained by using 100%-crystallinity.

According to the present invention, the amorphous carbon negative electrode material has certain pores to facilitate the exchange of lithium ions. Preferably, the Raman _Id / _Ig of the amorphous carbon in the negative electrode material is 1.01-1.1, and the specific surface area is 2 -15m ² /g, the pore volume is below 0.05cm ³ /g, and the average pore diameter is 1-10mm. More preferably, the negative electrode material has a specific surface area of 4-13m ² /g, a pore volume of 0.02cm ³ /g or less (preferably 0.005-0.016cm ³ /g), and an average pore diameter of 2-8mm (preferably 4 -6nm).

According to the present invention, the amorphous carbon negative electrode material has excellent rate performance and can obtain a higher specific capacity after the battery is manufactured. For example, after the amorphous carbon negative electrode material of the present invention is made into the standard measurement battery in the embodiment, the discharge specific capacity at 0.5C rate can be more than 250mAh/g, and the discharge specific capacity at 2C rate can be more than 130mAh/g .

The present invention also provides a method for preparing an amorphous carbon negative electrode material, the method comprising:

(1) In an oxygen-containing atmosphere, the coal-based pitch is subjected to a first heat treatment;

(2) subjecting the product after the first heat treatment to the second heat treatment in vacuum or under the first gas flow rate;

(3) subjecting the product after the second heat treatment to the third heat treatment in vacuum or under the second gas flow rate;

Wherein, the temperature of the first heat treatment<the temperature of the second heat treatment<the temperature of the third heat treatment; and, the temperature of the first heat treatment is 150-400°C, and the temperature of the second heat treatment The temperature of the treatment is 500-850°C, and the temperature of the third heat treatment is 800-1200°C;

The first gas flow rate and the second gas flow rate are each independently more than 30min ⁻¹ m ⁻² , and the gas flow rate is measured by volume space velocity per unit cross-sectional area; and, the first gas flow rate The gas introduced into the input volume and the second gas intake volume is an inert gas.

According to the present invention, the coal-based pitch can be a conventional coal-based pitch in the field. Compared with other types of pitch, such as petroleum-based pitch, the coal-based pitch has a higher density such as a density of 1.15 g/cm3 ^or more , and the aroma is higher (up to 55-80%), and the softening point is relatively high. Usually, the carbon element content of the coal-based pitch is 80-90% by weight, and the H/C molar ratio is 0.7-1.2.

The method of the present invention can make the coal-based asphalt be converted into performance by controlling the temperature of the first heat treatment, the second heat treatment and the third heat treatment and the gas feeding amount during the second heat treatment and the third heat treatment or to a vacuum. Excellent amorphous carbon anode material. Among them, it is worth mentioning that when the temperatures of the first heat treatment, the second heat treatment and the third heat treatment are lower than their lower limit values, the finally obtained amorphous carbon negative electrode material has the defect of low capacity. However, when the temperatures of the first heat treatment, the second heat treatment and the third heat treatment are higher than the upper limit, the capacity of the finally obtained amorphous carbon negative electrode material is also low.

In order to obtain an amorphous carbon negative electrode material with higher rate performance and specific capacity, preferably, the temperature of the first heat treatment is 180-350°C (preferably 200-300°C), and the temperature of the second heat treatment is 600-800°C (preferably 700-800°C), the temperature of the third heat treatment is 950-1200°C (preferably 1000-1100°C).

Wherein, in step (1), the coal-based pitch is subjected to the first heat treatment in an oxygen-containing atmosphere (such as an air atmosphere, an oxygen atmosphere, etc.), mainly to oxidize small molecules in the coal-based pitch. The time of the first heat treatment can be changed in a wide range, as long as the desired effect can be obtained, preferably, the time of the first heat treatment is more than 2h, preferably 3-20h, more preferably 5h -10h. It should be noted that if the time of the first heat treatment is less than 2h, the small molecules in the coal-based pitch may not be completely oxidized, so that large particles of amorphous carbon are easily obtained in the subsequent heat treatment. There is no benefit in improving the electrical properties of the resulting material.

Wherein, in step (2), in vacuum or under the first gas flow rate, the product after the first heat treatment is subjected to the second heat treatment, mainly in order to remove non-carbon elements, wherein, in order to improve the amorphous carbon To improve the structure of the material and better form the passage of lithium ions in and out of the carbon layer, the heat treatment can be carried out in vacuum or under a certain amount of gas flow. Wherein, in order to obtain an amorphous carbon negative electrode material with higher rate performance and specific capacity, preferably, the first gas flow rate is 30-250min ^-1 m ^-2 , more preferably 50-200min ^-1 m ^{- 2} . Herein, the gas feed rate is the volumetric space velocity meter per unit cross-sectional area, that is, the space velocity through which the equivalent cross-sectional area of the unit reaction vessel passes through (the space velocity refers to the volume of gas passing through a unit volume of sample per unit time. ).

According to the present invention, the time of the second heat treatment can be changed within a wide range, as long as the desired effect can be obtained, preferably, the time of the second heat treatment is more than 3 hours, preferably 2-10 hours , more preferably 2-8h.

Wherein, in step (3), in vacuum or under the second gas flow rate, the product after the second heat treatment is subjected to the third heat treatment mainly to remove the components that are not conducive to the diffusion of lithium ions, wherein, Similarly, in order to improve the structure of the amorphous carbon material and better form the passage of lithium ions in and out of the carbon layer, the heat treatment can be performed in vacuum or with a certain gas flow rate. For this reason, in order to obtain an amorphous carbon negative electrode material with higher rate performance and specific capacity, preferably, the second gas flow rate is 30-250min ^-1 m ^-2 , more preferably 50-200min ^-1 m ^-2 .

According to the present invention, the time of the third heat treatment can be changed within a wide range, as long as the desired effect can be obtained, preferably, the time of the third heat treatment is more than 2 hours, preferably 3-15 hours , more preferably 4-10h.

According to the present invention, the inert gas is a gas which does not have an adverse effect on the resulting amorphous carbon under the reaction conditions of the present invention. Generally, the inert gas may be one or more of nitrogen, helium, neon and the like.

According to the present invention, the method of the present invention may also include ball milling the product after the second heat treatment and then performing the third heat treatment. The time of the ball milling may be, for example, 2-60 minutes, preferably 2-10 minutes. After ball milling, The large-particle materials in the product after the second heat treatment are ball-milled to a smaller particle size, for example, all particles with a D50 greater than 50 μm are ground.

The invention also provides the amorphous carbon negative electrode material prepared by the above method. Although the present invention has no particular limitation on the amorphous carbon negative electrode material, as long as it is prepared by the above method. However, through the above method, the amorphous carbon negative electrode material usually prepared has the properties of the amorphous carbon negative electrode material described above, so the corresponding description above is incorporated here and will not be repeated here.

By adopting the method of the invention, the coal-based pitch can be converted into an amorphous carbon negative electrode material with excellent performance, and the obtained amorphous carbon negative electrode material has excellent rate performance, and also has relatively high specific capacity and rate performance.

The present invention also provides a battery comprising the above-mentioned amorphous carbon negative electrode material.

The battery of the present invention can be prepared by the method shown in the examples, and its specific discharge capacity at 0.5C rate can be more than 250mAh/g, and its discharge specific capacity at 2C rate can be more than 130mAh/g.

The present invention will be described in detail below by way of examples.

In the following examples and comparative examples:

The XRD spectrum is radiated by a Bruker D8Advance diffractometer (Bruker), the tube voltage is 40kV, the tube current is 40mA, and the X-ray radiation source is Cu Kα The acquisition step is 0.02°, and the acquisition 2θ range is 10-60°.

The Raman spectrum adopts HORIBA LabRAM HR Raman spectrometer, the laser wavelength is 532.06nm, the slit width is 100m, and the scanning range is 700～2100cm ^-1 .

The particle size test is carried out by Malvern laser particle size analyzer 2000, and the particle size range is: 0.020-2000μm.

The specific surface area was measured with a Quadrasorb SI _N2 adsorption-desorption instrument from Quanta Company.

The preparation process of the button battery is as follows: the negative electrode material/conductive carbon black Super P/binder prepared in the example is mixed with the solvent N-methylpyrrolidone (NMP) in a mass ratio of 92:3:5 to form a uniform negative electrode Slurry, and then use the scraper technique to evenly coat the negative electrode slurry on the copper foil, and then place it in an oven at 80°C for 24 hours in a vacuum. After the solvent is evaporated, use a punching machine to punch a negative electrode sheet with a diameter of 12mm. , then, dry the negative electrode sheet at 80°C for 24h, transfer it to MBraun2000 glove box (Ar atmosphere, H ₂ O and O ₂ concentration less than 0.1×10 ^-16 vol%), and assemble it into a button cell for reference electrode Lithium sheet.

The capacity is tested by CT2001 battery tester (Landian Electronics Co., Ltd.) for charge and discharge performance. The charge and discharge voltage range is between 0.0 and 3.0V, and the rate of 0.2C (1C=370mAh/g) is constant current charge and constant current discharge.

For the first time, CT2001 battery tester (Landian Electronics Co., Ltd.) was used to test the charge and discharge performance. The charge and discharge voltage range is between 0.0 and 3.0V. .

The 2C capacity uses CT2001 battery tester (Landian Electronics Co., Ltd.) to test the charge and discharge performance. The charge and discharge voltage range is between 0.0 and 3.0V, and the rate of 2C (1C=370mAh/g) is constant current charge and constant current discharge.

Coal-based asphalt is the coal-based asphalt of Shenhua Group, with a C content of >85% and a softening point of >300°C.

Example 1

This example is used to illustrate the amorphous carbon negative electrode material of the present invention and its preparation method.

(1) Heating the coal-based pitch at 250°C for 6 hours in an air atmosphere;

(2) Then heat at 750°C and 200min ^-1 m ^-2 nitrogen atmosphere for 3h;

(3) The product obtained in step (2) was taken out and ball-milled for 5 minutes; finally heated at 1050° C. and 200 min ⁻¹ m ⁻² nitrogen atmosphere for 6 hours.

The finally obtained amorphous carbon has a degree of amorphism of 23%, a specific surface area of 5m ² /g, a pore volume of 0.01cm ³ /g, an average pore diameter of 6nm, and a Raman _Id / _Ig of 1.038; After the shaped carbon is used as the negative electrode material to make a button battery, the electrochemical performance test is carried out. The results: the discharge specific capacity at 0.5C rate is 267mAh/g, the first Coulombic efficiency is 82.5%, and the discharge specific capacity at 2C rate is 135mAh/g .

Example 2

This example is used to illustrate the amorphous carbon negative electrode material of the present invention and its preparation method.

According to the method described in Example 1, the difference is that the feeding amount of nitrogen in step (2) is 100 min ^-1 m ^-2 , and the feeding amount of nitrogen in step (3) is 100 min ^-1 m ^-2 .

The finally obtained amorphous carbon has a degree of amorphism of 23.8%, a specific surface area of 4m ² /g, a pore volume of 0.008cm ³ /g, an average pore diameter of 4nm, and a Raman _Id / _Ig of 1.047; After the shaped carbon was used as the negative electrode material to make a button battery, the electrochemical performance test was carried out. The results: the discharge specific capacity at 0.5C rate was 261mAh/g, the first Coulombic efficiency was 82.0%, and the discharge specific capacity at 2C rate was 137mAh/g .

Example 3

This example is used to illustrate the amorphous carbon negative electrode material of the present invention and its preparation method.

According to the method described in Example 1, the difference is that the feeding amount of nitrogen in step (2) is 50 min ^-1 m ^-2 , and the feeding amount of nitrogen in step (3) is 50 min ^-1 m ^-2 .

The finally obtained amorphous carbon has a degree of amorphism of 22.8%, a specific surface area of 13m ² /g, a pore volume of 0.016cm ³ /g, an average pore diameter of 5nm, and a Raman _Id / _Ig of 1.041; After the shaped carbon is used as the negative electrode material to make a button battery, the electrochemical performance test is carried out. The results: the discharge specific capacity at 0.5C rate is 258mAh/g, the first Coulombic efficiency is 81.8%, and the discharge specific capacity at 2C rate is 131mAh/g .

Example 4

This example is used to illustrate the amorphous carbon negative electrode material of the present invention and its preparation method.

According to the method described in Example 1, the difference is that the step (2) is calcined in a vacuum state, and the step (3) is calcined in a vacuum.

The finally obtained amorphous carbon has a degree of amorphism of 24.8%, a specific surface area of 6m ² /g, a pore volume of 0.006cm ³ /g, an average pore diameter of 6nm, and a Raman _Id / _Ig of 1.024; The electrochemical performance test was carried out after the shaped carbon was used as the negative electrode material to make a button battery. The results: the discharge specific capacity at 0.5C rate was 272mAh/g, the first Coulombic efficiency was 83.4%, and the discharge specific capacity at 2C rate was 141mAh/g .

Example 5

This example is used to illustrate the amorphous carbon negative electrode material of the present invention and its preparation method.

According to the method described in Example 1, the difference is that the heat treatment temperature in step (1) is 320°C.

The final amorphous carbon was used as the negative electrode material to make a button battery and then the electrochemical performance test was performed. The result: the discharge specific capacity at 0.5C rate was 265mAh/g, the first coulombic efficiency was 80%, 2C The discharge specific capacity under the rate is 130mAh/g.

Comparative example 1

According to the method described in Example 1, the difference is that the feeding amount of nitrogen in step (2) is 10 min ^-1 m ^-2 , and the feeding amount of nitrogen in step (3) is 10 min ^-1 m ^-2 .

The finally obtained amorphous carbon has a degree of amorphism of 31%, a specific surface area of 7m ² /g, a pore volume of 0.01cm ³ /g, a pore diameter of 5.4nm, and a Raman _Id / _Ig of 1.09; The electrochemical performance test was carried out after the shaped carbon was used as the negative electrode material to make the electrode. The results: the discharge specific capacity at 0.5C rate was 233mAh/g, the first Coulombic efficiency was 80.2%, and the discharge specific capacity at 2C rate was 118mAh/g.

Comparative example 2

According to the method described in Example 1, the difference is that the temperature of the heat treatment in step (1) is 200°C, and the temperature of the heat treatment in step (3) is 950°C.

Finally, the amorphous carbon was obtained, and the amorphous carbon was used as the negative electrode material to make an electrode, and then the electrochemical performance test was carried out. The results: the discharge specific capacity at 0.5C rate was 195mAh/g, the first Coulombic efficiency was 79%, and the discharge capacity at 2C rate was 79%. The specific discharge capacity is 90mAh/g.

Comparative example 3

According to the method described in Example 1, the difference is that the feed rate of nitrogen in step (2) is 50min ⁻¹ m ⁻² ; the feed rate of nitrogen gas in step (3) is 50 min ⁻¹ m ⁻² , and The temperature of the heat treatment was 1500°C.

The finally obtained amorphous carbon has a degree of amorphism of 12.6%, a specific surface area of 1.3m ² /g, a pore volume of 0.006cm ³ /g, a pore diameter of 5nm, and a Raman _Id / _Ig of 0.98; the amorphous Electrochemical performance test was carried out after carbon was used as the negative electrode material. The results showed that the discharge specific capacity at 0.5C rate was 190mAh/g, the first Coulombic efficiency was 85.5%, and the discharge specific capacity at 2C rate was 77mAh/g.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention. These simple modifications All belong to the protection scope of the present invention.

In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way if there is no contradiction. The combination method will not be described separately.

In addition, various combinations of different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the idea of the present invention, they should also be regarded as the disclosed content of the present invention.

Claims (11)

1. a kind of agraphitic carbon negative material, which is characterized in that the unformed degree of the agraphitic carbon in the negative material is 18- 30%, Raman I_d/I_gFor 1.01-1.1.

2. agraphitic carbon negative material according to claim 1, wherein, agraphitic carbon in the negative material it is unformed It spends for 20-28%, preferably 22-25%；

Preferably, Raman I_d/I_gFor 1.02-1.05.

3. agraphitic carbon negative material according to claim 1 or 2, wherein, the ratio of the agraphitic carbon in the negative material Surface area is 2-15m²/ g, pore volume 0.05cm³/ g is hereinafter, average pore size is 1-10nm.

4. agraphitic carbon negative material according to claim 3, wherein, the specific surface of the agraphitic carbon in the negative material Product is 4-13m²/ g, pore volume 0.02cm³/ g is hereinafter, average pore size is 2-8nm.

5. a kind of preparation method of agraphitic carbon negative material, which is characterized in that this method includes：

(1) in oxygen-containing atmosphere, coal-based pitch is subjected to the first heat treatment；

(2) in a vacuum the product after the first heat treatment or under first gas intake, is subjected to the second heat treatment；

(3) in a vacuum the product after the second heat treatment or under second gas intake, is subjected to third heat treatment；

Wherein, the temperature of first heat treatment<The temperature of second heat treatment<The temperature of the third heat treatment Degree；Also, the temperature of first heat treatment is 150-400 DEG C, and the temperature of second heat treatment is 500-850 DEG C, The temperature of the third heat treatment is 800-1200 DEG C；

The first gas intake and second gas intake are each independently 30min^-1m^-2More than, the gas intake with The volume space velocity meter of unit cross-sectional area；Also, the gas that the first gas intake and second gas intake are passed through is Non-interactive gas.

6. according to the method described in claim 5, wherein, the temperature of first heat treatment is 180-350 DEG C, described second The temperature of heat treatment is 600-800 DEG C, and the temperature of the third heat treatment is 950-1200 DEG C.

7. method according to claim 5 or 6, wherein, the time of first heat treatment is more than 2h, preferably 3- 20h, more preferably 5-10h；

Preferably, the time of second heat treatment is more than 2h, more preferably preferably 2-10h, 2-8h；

Preferably, the time of the third heat treatment is more than 2h, more preferably preferably 3-15h, 4-10h.

8. according to the method described in any one in claim 5-7, wherein, the first gas intake is 30-250min^{- 1}m^-2, more preferably 50-200min^-1m^-2；

Preferably, the second gas intake is 30-250min^-1m^-2, more preferably 50-200min^-1m^-2。

9. according to the method described in any one in claim 5-8, wherein, this method further includes will be after the second heat treatment Product carries out third heat treatment again after carrying out ball milling, and the time of the ball milling is 2-60min.

10. the agraphitic carbon negative material that the method in claim 5-9 described in any one is prepared.

11. include the battery of agraphitic carbon negative material according to any one of claims 10.